JP2008064733A - Apparatus and method of estimating sound source direction, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately estimate a direction where a sound source is located, even if there is ambient noise during sound inputting from a microphone. <P>SOLUTION: Acoustic signals from sound sources located in a plurality of directions are received as inputs of a plurality of channels (S301), and converted into signals on a frequency axis (S303). Phase components on the converted signals on the frequency axis are calculated for the same frequency, and the phase differences among the plurality of channels are calculated (S304). Meanwhile, amplitude components on the converted frequency axis are calculated (S305), and noise components are estimated from the calculated amplitude components (S306). The SN ratio for each frequency is calculated based on the amplitude components and noise components (S307), and the frequency with the SN ratio which is larger than a predetermined value is selected (S308). Difference in longitudinal coverage is calculated, based on the phase difference of the selected frequency (S310), and the direction where the sound source of interest is estimated as existing is calculated (S311). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sound source direction estimation device, a sound source direction estimation method, and a computer that can estimate the arrival direction of sound input from a sound source with high accuracy even when ambient noise exists using a plurality of microphones. Regarding the program.

  With recent advances in computer technology, even acoustic signal processing that requires a large amount of arithmetic processing can be executed at a practical processing speed. Under such circumstances, the practical application of a multi-channel sound processing function using a plurality of microphones is expected. One example is sound source direction estimation processing for estimating the arrival direction of an acoustic signal. In the sound source direction estimation process, a plurality of microphones are installed, the delay time when the acoustic signal from the target sound source reaches the two microphones is obtained, and the difference in the arrival distance between the microphones and the microphone installation interval are calculated. This is a process for estimating the direction of arrival of the acoustic signal from the sound source based on the sound source.

  In the conventional sound source direction estimation process, for example, a cross-correlation between signals input from two microphones is calculated, and a delay time between the two signals at a time when the cross-correlation is maximized is calculated. By multiplying the calculated delay time by about 340 m / s, which is the propagation speed of sound in air at room temperature (which varies depending on the temperature), the difference in reach can be obtained. The direction of arrival of the acoustic signal is calculated according to the method.

Further, as disclosed in Patent Document 1, a phase difference spectrum for each frequency of an acoustic signal input from two microphones is calculated, and based on the slope of the phase difference spectrum when linearly approximating to a frequency base, It is also possible to calculate the direction of arrival of the acoustic signal from the sound source.
JP 2003-337164 A

  In the conventional sound source direction estimation method described above, it is difficult to specify the time when the cross-correlation is maximized when noise is superimposed. This causes a problem that it is difficult to correctly specify the arrival direction of the acoustic signal from the sound source. Even in the method disclosed in Patent Document 1, when calculating the phase difference spectrum, the phase difference spectrum fluctuates drastically when noise is superimposed. There was a problem that could not be asked.

  The present invention has been made in view of the above circumstances, and estimates the arrival direction of an acoustic signal from a target sound source with high accuracy even when ambient noise exists around the microphone. An object is to provide a sound source direction estimating apparatus, a sound source direction estimating method, and a computer program.

  In order to achieve the above object, a sound source direction estimating apparatus according to a first aspect of the present invention receives an acoustic signal from a sound source existing in a plurality of directions as an input of a plurality of channels, and converts the sound signal into a signal on a time axis for each channel. Means, signal converting means for converting each signal on the time axis converted by the acoustic signal receiving means to a signal on the frequency axis for each channel, and each channel on the frequency axis converted by the signal converting means A phase component calculation unit that calculates a phase component of the signal for each same frequency, and a phase difference between a plurality of channels is calculated using the phase component of the signal of each channel calculated for each same frequency by the phase component calculation unit. Based on the phase difference calculation means and the phase difference calculated by the phase difference calculation means, the difference in the reach of the acoustic signal from the target sound source is calculated. A sound source direction estimating device comprising: a distance difference calculating unit that calculates a direction in which a target sound source exists based on a difference in distance calculated by the distance difference calculating unit. Amplitude component calculating means for calculating the amplitude component of the signal on the frequency axis converted by the signal converting means, noise component estimating means for estimating a noise component from the amplitude component calculated by the amplitude component calculating means, A signal-to-noise ratio calculating unit that calculates a signal-to-noise ratio for each frequency based on the amplitude component calculated by the amplitude component calculating unit and the noise component estimated by the noise component estimating unit; and the signal-to-noise ratio calculating unit And a frequency extraction means for extracting a frequency with a signal-to-noise ratio calculated by a value greater than a predetermined value. Characterized in that based on the phase difference of the frequency extracted by the stage are to calculate the difference between the arrival distances.

  Further, in the sound source direction estimating apparatus according to the second invention, in the first invention, the frequency extracting means calculates a frequency at which the signal to noise ratio calculated by the signal to noise ratio calculating means is larger than a predetermined value. A predetermined number is selected and extracted in descending order of the signal-to-noise ratio.

  Further, the sound source direction estimating device according to the third aspect of the invention receives an acoustic signal from a sound source existing in a plurality of directions as an input of a plurality of channels, and converts the sound signal receiving means for converting the sampling signal on the time axis for each channel, Signal conversion means for converting each sampling signal on the time axis converted by the acoustic signal receiving means to a signal on the frequency axis for each channel, and the phase of the signal of each channel on the frequency axis converted by the signal conversion means Phase component calculation means for calculating components for each same frequency, and phase difference calculation for calculating a phase difference between a plurality of channels using the phase component of each channel signal calculated for each same frequency by the phase component calculation means. Difference of the reach of the acoustic signal from the target sound source based on the phase difference calculated by the means and the phase difference calculation means A sound source direction estimation device comprising: a calculated reach distance difference calculating means; and a sound source direction estimating means for estimating a direction in which a target sound source exists based on the reach distance difference calculated by the reach distance difference calculating means An amplitude component calculating means for calculating an amplitude component of the signal on the frequency axis converted at a predetermined sampling time by the signal converting means, and noise for estimating a noise component from the amplitude component calculated by the amplitude component calculating means Component estimation means; signal-to-noise ratio calculation means for calculating a signal-to-noise ratio for each frequency based on the amplitude component calculated by the amplitude component calculation means and the noise component estimated by the noise component estimation means; and Sampling based on the signal-to-noise ratio calculated by the signal-to-noise ratio calculation means and the phase difference calculation result at the past sampling time Correction means for correcting the calculation result of the phase difference at the point, and the reaching distance difference calculating means calculates the difference of the reaching distance based on the phase difference after correction by the correcting means. It is characterized by.

  According to a fourth aspect of the present invention, there is provided the sound source direction estimating apparatus according to any one of the first to third aspects, wherein a sound section that is a section indicating sound in the sound signal input received by the sound signal receiving means. A voice section specifying means for specifying is further provided, wherein the signal converting means converts only the signal of the voice section specified by the voice section specifying means into a signal on the frequency axis.

  The sound source direction estimating method according to the fifth aspect of the present invention includes a step of receiving sound signals from sound sources existing in a plurality of directions as inputs of a plurality of channels, converting the signals into signals on the time axis for each channel, A step of converting the signal of the channel into a signal on the frequency axis, a step of calculating the phase component of the converted signal of each channel on the frequency axis for each same frequency, and a signal of each channel calculated for each same frequency Calculating a phase difference between a plurality of channels using the phase component, calculating a difference in reach of an acoustic signal from a target sound source based on the calculated phase difference, and calculating A sound source direction estimation method including a step of estimating a direction in which a target sound source is present based on a difference in reach distance on a converted frequency axis Calculating an amplitude component of the signal; estimating a noise component from the calculated amplitude component; calculating a signal-to-noise ratio for each frequency based on the calculated amplitude component and the estimated noise component; Extracting a frequency having a signal-to-noise ratio larger than a predetermined value, and calculating the difference in reach distance calculates the difference in reach distance based on the phase difference in the extracted frequency. It is characterized by.

  The sound source direction estimation method according to the sixth aspect of the invention includes a step of receiving acoustic signals from sound sources existing in a plurality of directions as inputs of a plurality of channels and converting them into sampling signals on the time axis for each channel; A step of converting each sampling signal into a signal on the frequency axis for each channel, a step of calculating a phase component of each channel signal on the converted frequency axis for each same frequency, and each step calculated for each same frequency A step of calculating a phase difference between a plurality of channels using a phase component of a signal of a channel, a step of calculating a difference in reach of an acoustic signal from a target sound source based on the calculated phase difference; A sound source direction estimating method including a step of estimating a direction in which a target sound source exists based on the calculated difference in reach distance And calculating the amplitude component of the signal on the frequency axis converted at a predetermined sampling time, estimating the noise component from the calculated amplitude component, and calculating the calculated amplitude component and the estimated noise component. Based on the step of calculating the signal-to-noise ratio for each frequency based on the calculated signal-to-noise ratio and the calculation result of the phase difference at the past sampling time, the calculation result of the phase difference at the sampling time is corrected The step of calculating the difference in reach distance includes calculating the difference in reach distance based on the corrected phase difference.

  The computer program according to the seventh invention can be executed by a computer, and the computer receives sound signals from a sound source existing in a plurality of directions as inputs of a plurality of channels, and is on a time axis for each channel. An acoustic signal receiving means for converting to a signal, a signal converting means for converting a signal of each channel on the time axis into a signal on the frequency axis, and calculating a phase component of each channel signal on the converted frequency axis for each same frequency Phase component calculation means for performing phase difference calculation means for calculating a phase difference between a plurality of channels using a phase component of each channel signal calculated for each same frequency, and based on the calculated phase difference Based on the reach distance difference calculating means for calculating the difference of the reach distance of the acoustic signal from the sound source, and the calculated reach distance difference, In a computer program for functioning as a sound source direction estimating means for estimating a direction in which a target sound source exists, an amplitude component calculating means for calculating an amplitude component of a signal on a converted frequency axis, a calculated amplitude component Noise component estimating means for estimating a noise component from the signal, a signal-to-noise ratio calculating means for calculating a signal-to-noise ratio for each frequency based on the calculated amplitude component and the estimated noise component, and a calculated signal-to-noise ratio Function as a frequency extraction means for extracting a frequency greater than a predetermined value, and the function as the reach distance difference calculation means is based on the phase difference of the frequency extracted by the function as the frequency extraction means. The difference is calculated.

  The computer program according to the eighth aspect of the invention can be executed by a computer, and the computer accepts sound signals from sound sources existing in a plurality of directions as inputs of a plurality of channels on a time axis for each channel. Acoustic signal receiving means for converting to signal, signal converting means for converting each sampling signal on the time axis into a signal on the frequency axis for each channel, and phase component of each channel signal on the converted frequency axis for each same frequency A phase component calculating means for calculating a phase difference between a plurality of channels using a phase component of each channel signal calculated for each same frequency, and a purpose based on the calculated phase difference. A reach distance difference calculating means for calculating the difference in reach of acoustic signals from the sound source, and the calculated reach distance In a computer program that functions as sound source direction estimation means for estimating the direction in which a target sound source exists based on the minutes, the computer calculates the amplitude component of the signal on the frequency axis converted at a predetermined sampling time Amplitude component calculation means, noise component estimation means for estimating a noise component from the calculated amplitude component, signal-to-noise ratio calculation for calculating a signal-to-noise ratio for each frequency based on the calculated amplitude component and the estimated noise component Means for correcting the calculation result of the phase difference at the sampling time based on the calculated signal-to-noise ratio and the calculation result of the phase difference at the past sampling time, As a function of calculating the difference in the reach based on the phase difference after correction by the function as the correction means. It characterized that you have way.

  In the first invention, the fifth invention, and the seventh invention, acoustic signals from sound sources existing in a plurality of directions are received as inputs of a plurality of channels and converted into signals on the time axis for each channel. Furthermore, the signal of each channel on the time axis is converted into a signal on the frequency axis, and the phase component of the signal of each channel on the frequency axis that has been converted is used, so that the phase difference between multiple channels can be changed for each frequency. Calculated. Based on the calculated phase difference (hereinafter also referred to as a phase difference spectrum), the difference in the reach distance of the sound input from the target sound source is calculated, and the sound source exists based on the calculated difference in the reach distance. The direction is estimated. On the other hand, the amplitude component of the converted signal on the frequency axis is calculated, and the background noise component is estimated from the calculated amplitude component. A signal-to-noise ratio for each frequency is calculated based on the calculated amplitude component and the estimated background noise component. Then, a frequency having a signal-to-noise ratio larger than a predetermined value is extracted, and a difference in reach is calculated based on the phase difference between the extracted frequencies. As a result, a signal-to-noise ratio (SN ratio) for each frequency based on the amplitude component of the input acoustic signal, so-called amplitude spectrum, and the estimated background noise component, so-called background noise spectrum. Therefore, by using only the phase difference at a frequency with a large signal-to-noise ratio, it is possible to obtain a more accurate difference in reachable distance. Therefore, it is possible to estimate the incident angle of the acoustic signal, that is, the direction in which the sound source exists with high accuracy based on the difference in the arrival distance with high accuracy.

  In the second invention, a predetermined number of frequencies having a signal-to-noise ratio larger than a predetermined value are selected and extracted in descending order of the signal-to-noise ratio. As a result, since the frequency with a small influence degree of the noise component is sampled and the difference in the reach distance is calculated, the calculation result of the reach distance difference does not vary greatly. Therefore, the incident angle of the acoustic signal, that is, the direction in which the target sound source exists can be estimated with higher accuracy.

  In the third invention, the sixth invention, and the eighth invention, an acoustic signal from a sound source existing in a plurality of directions is accepted as an input of a plurality of channels, converted into a sampling signal on the time axis for each channel, and on the time axis. Each sampling signal is converted into a signal on the frequency axis for each channel. By using the phase component of the signal of each channel on the converted frequency axis, a phase difference between a plurality of channels is calculated for each frequency. Based on the calculated phase difference, the difference in the arrival distance of the sound input from the target sound source is calculated, and the direction in which the target sound source exists is estimated based on the calculated difference in the arrival distance. The amplitude component of the signal on the frequency axis converted at a predetermined sampling time is calculated, and the background noise component is estimated from the calculated amplitude component. A signal-to-noise ratio for each frequency is calculated based on the calculated amplitude component and the estimated background noise component. Then, the calculation result of the phase difference at the sampling time is corrected based on the calculated signal-to-noise ratio and the calculation result of the phase difference at the past sampling time, and the reach distance is calculated based on the corrected phase difference. The difference is calculated. As a result, it is possible to obtain a phase difference spectrum that reflects phase difference information at a frequency at which the signal-to-noise ratio at the past sampling time is large. For this reason, the phase difference does not vary greatly depending on the state of the background noise, the change in the content of the acoustic signal emitted from the target sound source, and the like. Therefore, it is possible to estimate the incident angle of the acoustic signal, that is, the direction in which the target sound source exists with high accuracy based on the difference in the arrival distance with higher accuracy and stability.

  In the fourth aspect of the invention, a voice section that is a section indicating voice in the received acoustic signal is specified, and only the signal in the specified voice section is converted into a signal on the frequency axis. As a result, it is possible to estimate with high accuracy the direction in which a sound source that emits sound exists.

  According to the first invention, the fifth invention, and the seventh invention, the signal-to-noise ratio (SN ratio) for each frequency based on the amplitude component of the input acoustic signal, so-called amplitude spectrum, and the estimated background noise spectrum. ) And only a phase difference (phase difference spectrum) at a frequency with a large signal-to-noise ratio can be used to obtain a more accurate difference in reachable distance. Therefore, it is possible to estimate the incident angle of the acoustic signal, that is, the direction in which the sound source exists with high accuracy based on the difference in the arrival distance with high accuracy.

  According to the second aspect of the present invention, the difference in the reach distance is calculated by preferentially selecting a frequency having a small influence of the noise component, so that the calculation result of the reach distance difference does not vary greatly. Therefore, the incident angle of the acoustic signal, that is, the direction in which the target sound source exists can be estimated with higher accuracy.

  According to the third invention, the sixth invention, and the eighth invention, when calculating the phase difference (phase difference spectrum) in order to obtain the difference of the reach distance, based on the phase difference calculated at the past sampling time point, The newly calculated phase difference can be corrected sequentially. The corrected phase difference spectrum also reflects the phase difference information at the frequency at which the signal-to-noise ratio at the past sampling time is large, so the background noise state, the acoustic signal emitted from the target sound source The phase difference does not vary greatly due to changes in the contents. Therefore, it is possible to estimate the incident angle of the acoustic signal, that is, the direction in which the target sound source exists with high accuracy based on the difference in the arrival distance with higher accuracy and stability.

  According to the fourth aspect of the present invention, it is possible to estimate with high accuracy the direction in which a sound source that emits sound, for example, a person exists.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. In the present embodiment, a case will be described in which an acoustic signal to be processed is mainly a voice emitted by a human.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a general-purpose computer that embodies a sound source direction estimating apparatus 1 according to Embodiment 1 of the present invention.

  A general-purpose computer that operates as the sound source direction estimating apparatus 1 according to the first embodiment of the present invention includes at least a calculation processing unit 11 such as a CPU and a DSP, a ROM 12, a RAM 13, and a communication interface unit capable of data communication with an external computer. 14, a plurality of voice input units 15, 15,... That receive voice input, and a voice output unit 16 that outputs voice. The voice output unit 16 outputs the voice input from the voice input unit 31 of the communication terminal devices 3, 3,... Capable of data communication via the communication network 2. In addition, the audio | voice output part 32 of communication terminal device 3,3, ... outputs the audio | voice which suppressed noise.

  The arithmetic processing unit 11 is connected to each hardware unit as described above of the sound source direction estimating apparatus 1 via the internal bus 17. The arithmetic processing unit 11 controls each part of the hardware described above, and estimates a noise component from the processing program stored in the ROM 12, for example, a program for calculating the amplitude component of the signal on the frequency axis, and the calculated amplitude component. Program, program that calculates the signal-to-noise ratio (Signal-to-Noise ratio) for each frequency based on the calculated amplitude component and the estimated noise component, and extracts frequencies that have an SN ratio greater than a predetermined value Various programs according to a program for calculating the distance of the arrival distance based on the phase difference of the extracted frequency (hereinafter referred to as phase difference spectrum), a program for estimating the direction of the sound source based on the difference of the arrival distance, etc. The functional function.

  The ROM 12 is configured by a flash memory or the like, and stores the above-described processing program necessary for causing the general-purpose computer to function as the sound source direction estimation device 1 and numerical information referred to by the processing program. The RAM 13 is composed of SRAM or the like, and stores temporary data generated when the program is executed. The communication interface unit 14 downloads the above-described program from an external computer, transmits output signals to the communication terminal devices 3, 3,... Via the communication network 2, and receives input acoustic signals.

  Specifically, each of the sound input units 15, 15,... Is a microphone that receives sound, and includes a plurality of microphones, amplifiers, A / D converters, and the like to specify the direction of the sound source. The audio output unit 16 is an output device such as a speaker. For convenience of explanation, FIG. 1 shows that the sound input unit 15 and the sound output unit 16 are built in the sound source direction estimating apparatus 1. However, in practice, the sound source direction estimating device 1 is configured by connecting the sound input unit 15 and the sound output unit 16 to a general-purpose computer via an interface.

  FIG. 2 is a block diagram showing functions realized when the arithmetic processing unit 11 of the sound source direction estimating apparatus 1 according to Embodiment 1 of the present invention executes the processing program as described above. In the example shown in FIG. 2, a case will be described in which each of the two sound input units 15 and 15 is a single microphone.

  As shown in FIG. 2, the sound source direction estimation device 1 according to Embodiment 1 of the present invention includes at least a voice reception unit (acoustic signal reception unit) 201 as functional blocks realized when a processing program is executed. Signal conversion unit (signal conversion unit) 202, phase difference spectrum calculation unit (phase difference calculation unit) 203, amplitude spectrum calculation unit (amplitude component calculation unit) 204, background noise estimation unit (noise component estimation unit) 205, SN ratio calculation A unit (signal-to-noise ratio calculation unit) 206, a phase difference spectrum selection unit (frequency extraction unit) 207, a reach distance difference calculation unit (reach distance difference calculation unit) 208, and a sound source direction estimation unit (sound source direction estimation unit) 209. I have.

  The voice receiving unit 201 receives voices uttered by a human being as a sound source as voice inputs from two microphones. In the present embodiment, input 1 and input 2 are received via audio input units 15 and 15 which are microphones, respectively.

  The signal conversion unit 202 converts a signal on the time axis into signals on the frequency axis, that is, spectra IN1 (f) and IN2 (f) for the input voice. Here, f indicates a frequency (radian). In the signal conversion unit 202, for example, time-frequency conversion processing such as Fourier transform is executed. In the first embodiment, the input speech is converted into spectra IN1 (f) and IN2 (f) by time-frequency conversion processing such as Fourier transform.

  The phase difference spectrum calculation unit 203 calculates a phase spectrum based on the frequency-converted spectra IN1 (f) and IN2 (f), and calculates a phase difference spectrum DIFF_PHASE (f) that is a phase difference between the calculated phase spectra. Calculate for each frequency. Further, the phase difference spectrum DIFF_PHASE (f) may be obtained by obtaining the phase component of IN1 (f) / IN2 (f) instead of obtaining the phase spectra of the spectra IN1 (f) and IN2 (f). . Here, the amplitude spectrum calculation unit 204 calculates an amplitude spectrum | IN1 (f) | that is an amplitude component of the input signal spectrum IN1 (f) of the input 1 in one of the examples shown in FIG. Which amplitude spectrum is calculated is not particularly limited. The amplitude spectrum | IN1 (f) | and | IN2 (f) | may be calculated, and the larger value may be selected.

  In the first embodiment, a configuration is employed in which the amplitude spectrum | IN1 (f) | is calculated for each frequency in the spectrum subjected to Fourier transform. However, the first embodiment may be configured such that band division is performed and a representative value of the amplitude spectrum | IN1 (f) | is obtained within a divided band divided by a specific center frequency and interval. In this case, the representative value may be an average value of the amplitude spectrum | IN1 (f) | in the divided band, or may be a maximum value. The representative value of the amplitude spectrum after the band division is | IN1 (n) |. Here, n indicates an index of the divided band.

  The background noise estimation unit 205 estimates the background noise spectrum | NOISE1 (f) | based on the amplitude spectrum | IN1 (f) |. The estimation method of the background noise spectrum | NOISE1 (f) | is not particularly limited. It is possible to use a known method such as a voice section detection process in voice recognition or a background noise estimation process performed in a noise canceller process used in a mobile phone or the like. In other words, any method for estimating the background noise spectrum can be used. As described above, when the amplitude spectrum is divided into bands, the background noise spectrum | NOISE1 (n) | may be estimated for each divided band. Here, n indicates an index of the divided band.

The SN ratio calculation unit 206 calculates a ratio between the amplitude spectrum | IN1 (f) | calculated by the amplitude spectrum calculation unit 204 and the background noise spectrum | NOISE1 (f) | estimated by the background noise estimation unit 205. As a result, the SN ratio SNR (f) is calculated. The SN ratio SNR (f) is calculated by the following equation (1). When the amplitude spectrum is band-divided, SNR (n) may be calculated for each divided band. Here, n indicates an index of the divided band.
SNR (f) = 20.0 × log ₁₀ (| IN1 (f) | / | NOISE1 (f) |) (1)

  The phase difference spectrum selection unit 207 extracts the frequency or frequency band in which the SN ratio larger than the predetermined value is calculated by the SN ratio calculation unit 206, and the phase difference spectrum corresponding to the extracted frequency or within the extracted frequency band Select the phase difference spectrum.

  The reach distance difference calculation unit 208 obtains a function that linearly approximates the relationship between the selected phase difference spectrum and the frequency f. Based on this function, the reach distance difference calculation unit 208 calculates the difference in distance between the sound source and both the sound input units 15 and 15, that is, the distance difference D until the sound reaches the both sound input units 15 and 15, respectively. Is calculated.

  The sound source direction estimation unit 209 uses the distance difference D calculated by the reach distance difference calculation unit 208 and the installation interval L of both the voice input units 15 and 15 to have an incident angle θ of the voice input, that is, a person who is a sound source. Then, an angle θ indicating the estimated direction is calculated.

  Hereinafter, a processing procedure executed by the arithmetic processing unit 11 of the sound source direction estimating apparatus 1 according to Embodiment 1 of the present invention will be described. FIG. 3 is a flowchart showing a processing procedure executed by the arithmetic processing unit 11 of the sound source direction estimating apparatus 1 according to Embodiment 1 of the present invention.

  First, the arithmetic processing unit 11 of the sound source direction estimating apparatus 1 receives an acoustic signal (analog signal) from the voice input units 15 and 15 (step S301). The arithmetic processing unit 11 performs A / D conversion on the received acoustic signal, and then frames the obtained sample signal in predetermined time units (step S302). At this time, in order to obtain a stable spectrum, a framed sample signal is multiplied by a time window such as a hamming window or a hanning window. The unit of framing is determined by the sampling frequency, the type of application, and the like. For example, framing is performed in units of 20 ms to 40 ms while overlapping by 10 ms to 20 ms, and the following processing is executed for each frame.

  The arithmetic processing unit 11 converts the signal on the time axis in units of frames into signals on the frequency axis, that is, spectra IN1 (f) and IN2 (f) (step S303). Here, f indicates a frequency (radian). The arithmetic processing unit 11 executes time-frequency conversion processing such as Fourier transform, for example. In the first embodiment, the arithmetic processing unit 11 converts signals on the time axis in units of frames into spectra IN1 (f) and IN2 (f) by time-frequency conversion processing such as Fourier transform.

  Next, the arithmetic processing unit 11 calculates a phase spectrum using the real part and the imaginary part of the frequency-converted spectra IN1 (f) and IN2 (f), and is a phase difference between the calculated phase spectra. The phase difference spectrum DIFF_PHASE (f) is calculated for each frequency (step S304).

  On the other hand, the arithmetic processing unit 11 calculates an amplitude spectrum | IN1 (f) | that is an amplitude component of the input signal spectrum IN1 (f) of the input 1 (step S305).

However, it is not necessary to be limited to calculating the amplitude spectrum for the input signal spectrum IN1 (f) of the input 1. In addition, for example, the amplitude spectrum may be calculated for the input signal spectrum IN2 (f) of the input 2, or the average value or the maximum value of the amplitude spectra of both the inputs 1 and 2 may be calculated as a representative value of the amplitude spectrum. Also good. Here, a configuration is used in which the amplitude spectrum | IN1 (f) | is calculated for each frequency in the spectrum subjected to Fourier transform. However, band division is performed, and the amplitude is divided within a divided band divided by a specific center frequency and interval. A configuration for calculating a representative value of the spectrum | IN1 (f) | may be adopted. The representative value may be an average value of the amplitude spectrum | IN1 (f) | in the divided band, or may be a maximum value. Moreover, it is not necessary to be limited to the structure which calculates an amplitude spectrum, For example, the structure which calculates a power spectrum may be sufficient. In this case, the SN ratio SNR (f) is calculated by the following equation (2).
SNR (f) = 10.0 × log ₁₀ (| IN1 (f) | ² / | NOISE1 (f) | ² ) (2)

  The arithmetic processing unit 11 estimates the noise interval based on the calculated amplitude spectrum | IN1 (f) |, and the background noise spectrum | NOISE1 (f) based on the estimated amplitude spectrum | IN1 (f) | ) | Is estimated (step S306).

  However, the estimation method of the noise section need not be particularly limited. As a method for estimating the background noise spectrum | NOISE1 (f) |, for example, a speech interval detection process in speech recognition or a background noise estimation process performed in a noise canceller process used in a mobile phone or the like is used. It is possible to use the already known methods. In other words, any method for estimating the background noise spectrum can be used. For example, it is possible to perform voice / noise determination by estimating a background noise level using power information in all bands and obtaining a threshold value for determining voice / noise based on the estimated background noise level. is there. As a result, when it is determined as noise, the background noise spectrum | NOISE1 (f) | is corrected by correcting the background noise spectrum | NOISE1 (f) | using the amplitude spectrum | IN1 (f) | It is common to estimate.

  The arithmetic processing unit 11 calculates the SN ratio SNR (f) for each frequency or frequency band according to the equation (1) (equation (2) in the case of a power spectrum) (step S307). The arithmetic processing unit 11 selects a frequency or frequency band in which the calculated SN ratio is greater than a predetermined value (step S308). The selected frequency or frequency band can be varied according to how the predetermined value is determined. For example, the SN ratio is compared between adjacent frequencies or frequency bands, and a frequency or frequency band having a maximum SN ratio is selected by sequentially selecting a frequency or frequency band having a larger SN ratio while being stored in the RAM 13. Can be selected. Further, the top N (N is a natural number) may be selected in descending order of SN ratio.

  The arithmetic processing unit 11 linearly approximates the relationship between the phase difference spectrum DIFF_PHASE (f) and the frequency f based on the phase difference spectrum DIFF_PHASE (f) corresponding to one or a plurality of selected frequencies or frequency bands (step) S309). As a result, it is possible to utilize the high reliability of the phase difference spectrum DIFF_PHASE (f) at a frequency or frequency band where the SN ratio is large. Thereby, the estimation accuracy of the proportional relationship between the phase difference spectrum DIFF_PHASE (f) and the frequency f can be increased.

FIG. 4 is a schematic diagram illustrating a method of correcting a phase difference spectrum when a frequency or frequency band having an SN ratio larger than a predetermined value is selected.
FIG. 4A shows a phase difference spectrum DIFF_PHASE (f) corresponding to a frequency or a frequency band. Usually, since background noise is superimposed, it is difficult to find a certain relationship.

  FIG. 4B shows the SN ratio SNR (f) within the frequency or frequency band. Specifically, a portion indicated by a double circle in FIG. 4B indicates a frequency or frequency band in which the SN ratio is larger than a predetermined value. Therefore, by selecting a frequency or frequency band having an S / N ratio larger than a predetermined value as shown in FIG. 4B, the phase difference spectrum DIFF_PHASE (f) corresponding to the selected frequency or frequency band is shown in FIG. In a), it becomes a portion indicated by a double circle. By linearly approximating the selected phase difference spectrum DIFF_PHASE (f) as shown in FIG. 4A, the phase difference spectrum DIFF_PHASE (f) and the frequency f are as shown in FIG. 4C. It can be seen that there is a proportional relationship.

  Therefore, the arithmetic processing unit 11 uses the Nyquist frequency F and the value of the phase difference spectrum DIFF_PHASE (π) linearly approximated at the Nyquist frequency F, that is, R in FIG. According to (3), the difference D of the reach distance of the sound input from the sound source is calculated (step S310). Note that the Nyquist frequency is half the sampling frequency, and is π in FIG. Specifically, when the sampling frequency is 8 kHz, the Nyquist frequency is 4 kHz.

FIG. 4C shows an approximate straight line obtained by approximating the selected phase difference spectrum DIFF_PHASE (f) with a straight line passing through the origin. However, if the characteristics of the microphones as the voice input units 15, 15,... Are different, the phase difference spectrum may be biased over the entire band. In such a case, the approximate line can be obtained by correcting the value R of the phase difference at the Nyquist frequency in consideration of the value corresponding to the frequency 0 of the approximate line, that is, the intercept value of the approximate line. .
D = (R × c) / (F × 2π) (3)

  The arithmetic processing unit 11 calculates the incident angle θ of the sound input, that is, the angle θ indicating the direction in which the sound source is estimated to exist, using the calculated distance D of the reached distance (step S311). FIG. 5 is a schematic diagram illustrating the principle of a method for calculating an angle θ indicating a direction in which a sound source is estimated to exist.

As shown in FIG. 5, the two voice input units 15 and 15 are installed with a distance L apart. In this case, there is a relationship of “sin θ = (D / L)” between the difference D in the reach distance of sound input from the sound source and the interval L between the two sound input units 15 and 15. Therefore, the angle θ indicating the direction in which the sound source is estimated to be present can be obtained by the following equation (4).
θ = sin ⁻¹ (D / L) (4)

  Even when N frequencies or frequency bands are selected in descending order of the SN ratio, linear approximation is performed using the top N phase difference spectra as described above. In addition, instead of using the value R of the phase difference spectrum DIFF_PHASE (F) that is linearly approximated at the Nyquist frequency F, the value of the phase difference spectrum r (= DIFF_PHASE (f)) at the selected frequency f is used. Substituting F and R in Equation (3) with f and r, respectively, calculating a difference D in reach for each selected frequency, and using the average value of the calculated differences D, it is estimated that a sound source exists. It is also possible to calculate the angle θ indicating the direction. Of course, it is not necessary to be limited to such a method. For example, the angle θ indicating the direction in which the sound source is estimated to be present may be calculated by performing weighting according to the SN ratio and calculating the representative value of the difference D of the reach distance.

  In addition, when estimating the direction in which a person who emits speech is present, it is determined whether or not the sound input is a speech section indicating the speech emitted by the person, and only when the speech input is determined to be a speech section. By executing the above process, the angle θ indicating the direction in which the sound source is estimated to exist may be calculated.

  Furthermore, even if it is determined that the SN ratio is larger than the predetermined value, if the phase difference is not assumed in view of the usage state, usage conditions, etc. of the application, the corresponding frequency or frequency band Is preferably excluded from selection targets. For example, when the sound source direction estimating apparatus 1 according to the first embodiment is applied to a device that is supposed to speak from the front direction, such as a mobile phone, the direction θ in which it is estimated that the sound source exists with the front as 0 degrees. However, when it is calculated that θ <−90 degrees or 90 degrees <θ, it is determined to be unexpected.

  Even if it is determined that the SN ratio is larger than a predetermined value, a frequency or a frequency band that is not preferable for estimating the direction of the target sound source in consideration of the use state, use conditions, etc. of the application. Is preferably excluded from selection targets. For example, when the target sound source is a voice produced by a human, there is no voice signal at a frequency of 100 Hz or less. Therefore, 100 Hz or less can be excluded from selection targets.

  As described above, the sound source direction estimating apparatus 1 according to the first embodiment is based on the amplitude component of the input acoustic signal, so-called amplitude spectrum, and the SN for each frequency or frequency band based on the estimated background noise spectrum. By calculating the ratio and using the phase difference (phase difference spectrum) at a frequency with a large S / N ratio, the more accurate difference D of the reachable distance can be obtained. Therefore, the incident angle of the acoustic signal, that is, the angle θ indicating the direction in which it is estimated that the target sound source (human in the first embodiment) exists is calculated with high accuracy based on the difference D of the reach distance with high accuracy. It becomes possible.

(Embodiment 2)
Hereinafter, a sound source direction estimating apparatus 1 according to Embodiment 2 of the present invention will be described in detail with reference to the drawings. Since the configuration of the general-purpose computer that operates as the sound source direction estimation apparatus 1 according to Embodiment 2 of the present invention is the same as that of Embodiment 1, detailed description will be given with reference to the block diagram shown in FIG. Omitted. In the second embodiment, the calculation result of the phase difference spectrum in units of frames is stored, and based on the stored previous phase difference spectrum and the SN ratio in the calculation target frame, the position in the calculation target frame is stored. This is different from the first embodiment in that a configuration for correcting the phase difference spectrum as needed is adopted.

  FIG. 6 is a block diagram illustrating functions realized when the arithmetic processing unit 11 of the sound source direction estimating apparatus 1 according to Embodiment 2 of the present invention executes a processing program. In the example illustrated in FIG. 6, the case where the voice input units 15 and 15 are configured by two microphones will be described as in the first embodiment.

  As shown in FIG. 6, the sound source direction estimation device 1 according to Embodiment 2 of the present invention has at least a voice reception unit (acoustic signal reception unit) 201 as a functional block realized when a processing program is executed. Signal conversion unit (signal conversion unit) 202, phase difference spectrum calculation unit (phase difference calculation unit) 203, amplitude spectrum calculation unit (amplitude component calculation unit) 204, background noise estimation unit (noise component estimation unit) 205, SN ratio calculation Unit (signal-to-noise ratio calculating unit) 206, phase difference spectrum correcting unit (correcting unit) 210, reaching distance difference calculating unit (arriving distance difference calculating unit) 208, and sound source direction estimating unit (sound source direction estimating unit) 209. ing.

  The voice receiving unit 201 receives a voice input from a person who is a sound source from two microphones. In the present embodiment, input 1 and input 2 are received via audio input units 15 and 15 which are microphones, respectively.

  The signal conversion unit 202 converts a signal on the time axis into signals on the frequency axis, that is, spectra IN1 (f) and IN2 (f) for the input voice. Here, f indicates a frequency (radian). In the signal conversion unit 202, for example, time-frequency conversion processing such as Fourier transform is executed. In the second embodiment, the input speech is converted into spectra IN1 (f) and IN2 (f) by time-frequency conversion processing such as Fourier transform.

  In addition, the audio | voice received by the audio | voice input parts 15 and 15 is A / D converted, and the obtained sample signal is framed by a predetermined time unit. At this time, in order to obtain a stable spectrum, a framed sample signal is multiplied by a time window such as a hamming window or a hanning window. The unit of framing is determined by the sampling frequency, the type of application, and the like. For example, framing is performed in units of 20 ms to 40 ms while overlapping by 10 ms to 20 ms, and the following processing is executed for each frame.

  The phase difference spectrum calculation unit 203 calculates a phase spectrum in units of frames based on the frequency-converted spectra IN1 (f) and IN2 (f), and a phase difference spectrum DIFF_PHASE () that is a phase difference between the calculated phase spectra. f) is calculated in units of frames. Here, the amplitude spectrum calculation unit 204 calculates an amplitude spectrum | IN1 (f) | that is an amplitude component of the input signal spectrum IN1 (f) of the input 1 in one of the examples shown in FIG. Which amplitude spectrum is calculated is not particularly limited. The amplitude spectra | IN1 (f) | and | IN2 (f) | may be calculated, and the average value of both may be selected, or the larger value may be selected.

  The background noise estimation unit 205 estimates the background noise spectrum | NOISE1 (f) | based on the amplitude spectrum | IN1 (f) |. The estimation method of the background noise spectrum | NOISE1 (f) | is not particularly limited. It is possible to use a known method such as a voice section detection process in voice recognition or a background noise estimation process performed in a noise canceller process used in a mobile phone or the like. In other words, any method for estimating the background noise spectrum can be used.

  The SN ratio calculation unit 206 calculates a ratio between the amplitude spectrum | IN1 (f) | calculated by the amplitude spectrum calculation unit 204 and the background noise spectrum | NOISE1 (f) | estimated by the background noise estimation unit 205. As a result, the SN ratio SNR (f) is calculated. The SN ratio SNR (f) is calculated by the above-described equation (1).

The phase difference spectrum correction unit 210 corrects the SN ratio calculated by the SN ratio calculation unit 206 and the phase difference spectrum DIFF_PHASE _t calculated at the previous sampling time stored in the RAM 13 after being corrected by the phase difference spectrum correction unit 210. _{Based on −1} (f), the phase difference spectrum DIFF_PHASE _t (f) calculated at the next sampling time, that is, the current sampling time is corrected. At the current sampling time, the SN ratio and phase difference spectrum DIFF_PHASE _t (f) are calculated in the same manner as before, and then the correction coefficient α (0 ≦ α ≦ 1) set according to the SN ratio is used. Then, according to the following equation (5), the phase difference spectrum DIFF_PHASE _t (f) of the frame at the current sampling time is calculated.

Although details of the correction coefficient α will be described later, for example, a value corresponding to the SN ratio is stored in the ROM 12 together with each program as numerical information referred to by the processing program.
DIFF_PHASE _t (f) = α × DIFF_PHASE _t (f)
+ (1-α) × DIFF_PHASE _t-1 (f) (5)

  The reach distance difference calculation unit 208 obtains a function that linearly approximates the relationship between the corrected phase difference spectrum and the frequency f. Based on this function, the reach distance difference calculation unit 208 calculates the difference in distance between the sound source and both the sound input units 15 and 15, that is, the distance difference until the sound reaches the both sound input units 15 and 15, respectively. D is calculated.

  The sound source direction estimation unit 209 uses the distance difference D and the installation interval L between the sound input units 15 and 15 to input the incident angle θ of the sound input, that is, the angle indicating the direction in which it is estimated that a human being is a sound source exists. θ is calculated.

  Hereinafter, a processing procedure executed by the arithmetic processing unit 11 of the sound source direction estimating apparatus 1 according to Embodiment 2 of the present invention will be described. 7 and 8 are flowcharts showing a processing procedure executed by the arithmetic processing unit 11 of the sound source direction estimating apparatus 1 according to Embodiment 2 of the present invention.

  First, the arithmetic processing unit 11 of the sound source direction estimating apparatus 1 receives an acoustic signal (analog signal) from the voice input units 15 and 15 (step S701). The arithmetic processing unit 11 performs A / D conversion on the received acoustic signal, and then frames the obtained sample signal in predetermined time units (step S702). At this time, in order to obtain a stable spectrum, a framed sample signal is multiplied by a time window such as a hamming window or a hanning window. The unit of framing is determined by the sampling frequency, the type of application, and the like. For example, framing is performed in units of 20 ms to 40 ms while overlapping by 10 ms to 20 ms, and the following processing is executed for each frame.

  The arithmetic processing unit 11 converts the signal on the time axis in units of frames into signals on the frequency axis, that is, spectra IN1 (f) and IN2 (f) (step S703). Here, f indicates a frequency or a frequency band having a certain width at the time of sampling. The arithmetic processing unit 11 executes time-frequency conversion processing such as Fourier transform, for example. In the second embodiment, the arithmetic processing unit 11 converts a signal on the time axis in units of frames into spectra IN1 (f) and IN2 (f) by time-frequency conversion processing such as Fourier transform.

Next, the arithmetic processing unit 11 calculates a phase spectrum using the real part and the imaginary part of the frequency-converted spectra IN1 (f) and IN2 (f), and is a phase difference between the calculated phase spectra. The phase difference spectrum DIFF_PHASE _t (f) is calculated for each frequency or frequency band (step S704).

  On the other hand, the arithmetic processing unit 11 calculates an amplitude spectrum | IN1 (f) | that is an amplitude component of the input signal spectrum IN1 (f) of the input 1 (step S705).

  However, it is not necessary to be limited to calculating the amplitude spectrum for the input signal spectrum IN1 (f) of the input 1. In addition, for example, the amplitude spectrum may be calculated for the input signal spectrum IN2 (f) of the input 2, or the average value or maximum value of the amplitude spectra of both the inputs 1 and 2 may be calculated as a representative value of the amplitude spectrum. Also good. Moreover, it is not necessary to be limited to the structure which calculates an amplitude spectrum, For example, the structure which calculates a power spectrum may be sufficient.

  The arithmetic processing unit 11 estimates the noise interval based on the calculated amplitude spectrum | IN1 (f) |, and the background noise spectrum | NOISE1 (f) based on the estimated amplitude spectrum | IN1 (f) | ) | Is estimated (step S706).

  However, the estimation method of the noise section need not be particularly limited. Regarding the method of estimating the background noise spectrum | NOISE1 (f) |, for example, the background noise level is estimated using power information in the entire band, and the speech / noise is determined based on the estimated background noise level. It is possible to perform voice / noise determination by obtaining a threshold value for performing the above. As a result, when it is determined as noise, the background noise spectrum | NOISE1 (f) | is corrected by correcting the background noise spectrum | NOISE1 (f) | using the amplitude spectrum | IN1 (f) | Any method for estimating the background noise spectrum, such as estimation, may be used.

The arithmetic processing unit 11 calculates the SN ratio SNR (f) for each frequency or frequency band in accordance with the above equation (1) (step S707). Next, the arithmetic processing unit 11 determines whether or not the phase difference spectrum DIFF_PHASE _t-1 (f) at the previous sampling time is stored in the RAM 13 (step S708).

When it is determined that the phase difference spectrum DIFF_PHASE _t-1 (f) at the previous sampling time is stored (step S708: YES), the arithmetic processing unit 11 performs the calculated sampling time (current sampling time). The correction coefficient α corresponding to the S / N ratio is read from the ROM 12 (step S710). Note that a function representing the relationship between the SN ratio and the correction coefficient α may be incorporated in the program, and the correction coefficient α may be obtained by calculation.

FIG. 9 is a graph showing an example of the correction coefficient α corresponding to the SN ratio. In the example shown in FIG. 9, when the SN ratio is 0 (zero), the correction coefficient α is set to 0 (zero). This means that when the calculated SN ratio is 0 (zero), the calculated phase difference spectrum DIFF_PHASE _t (f) is not used, as can be understood from the above-described equation (5). This means that subsequent processing is performed by using the phase difference spectrum DIFF_PHASE _t-1 (f) as the current phase difference spectrum. Hereinafter, the correction coefficient α is set to monotonously increase as the SN ratio increases. In the region where the S / N ratio is 20 dB or more, the correction coefficient α is fixed to a maximum value αmax smaller than 1. Here, the reason why the maximum value αmax of the correction coefficient α is set to a value smaller than 1 is that the value of the phase difference spectrum DIFF_PHASE _t (f) is the value when noise with a high S / N ratio suddenly occurs. This is to prevent 100% substitution with the phase difference spectrum of noise.

The arithmetic processing unit 11 corrects the phase difference spectrum DIFF_PHASE _t (f) according to the above-described equation (5) using the correction coefficient α read from the ROM 12 in accordance with the SN ratio (step S711). Thereafter, the operation processing unit 11, a phase difference after correction at the sampling time of the latest stored in the RAM13 spectrum DIFF_PHASE _t-1 and (f), the phase difference spectrum DIFF_PHASE _t after correction at the current sampling time (f) is updated and stored (step S712).

If the arithmetic processing unit 11 determines that the phase difference spectrum DIFF_PHASE _t-1 (f) at the previous sampling time is not stored (step S708: NO), the phase difference spectrum DIFF_PHASE _t (at the current sampling time) It is determined whether or not f) is used (step S717). As a criterion for determining whether or not to use the phase difference spectrum DIFF_PHASE _t (f) at the current sampling time point, an acoustic signal from the target sound source such as the SN ratio of the entire band, the result of voice / noise determination, or the like is used. A criterion for determining whether or not the voice is uttered (speaking by a human) is used.

On the other hand, when the arithmetic processing unit 11 determines that the phase difference spectrum DIFF_PHASE _t (f) at the current sampling time is not used, that is, the possibility that an acoustic signal is emitted from the sound source is low (step S717: NO). The initial value of the predetermined phase difference spectrum is set as the phase difference spectrum at the current sampling time (step S718). In this case, the initial value of the phase difference spectrum is set to 0 (zero) over all frequencies, for example. However, the setting in step S718 need not be limited to this.

  Next, the arithmetic processing unit 11 stores the initial value of the phase difference spectrum in the RAM 13 as the phase difference spectrum at the current sampling time (step S719), and advances the processing to step S713.

The arithmetic processing unit 11 uses the phase difference spectrum DIFF_PHASE _t (f) at the current sampling time, that is, if it is determined that there is a high possibility that an acoustic signal is emitted from the sound source (step S717: YES), The phase difference spectrum DIFF_PHASE _t (f) at the time of sampling is stored in the RAM 13 (step S720), and the process proceeds to step S713.

  Next, the arithmetic processing unit 11 linearly approximates the relationship between the phase difference spectrum DIFF_PHASE (f) and the frequency f based on the phase difference spectrum DIFF_PHASE (f) stored in any of steps S712, S719, and S720 ( Step S713). As a result, when linear approximation is performed based on the corrected phase difference spectrum, the frequency or frequency band in which the S / N ratio was large (that is, the reliability was high) not only at the current sampling time but also at the past sampling time. The phase difference spectrum DIFF_PHASE (f) reflecting the phase difference information at can be used. Thereby, the estimation accuracy of the proportional relationship between the phase difference spectrum DIFF_PHASE (f) and the frequency f can be increased.

  Using the value R of the phase difference spectrum DIFF_PHASE (F) that is linearly approximated at the Nyquist frequency F, the arithmetic processing unit 11 calculates the difference D in the reach of the acoustic signal from the sound source according to the above-described equation (3). (Step S714). However, even if the value R of the phase difference spectrum r (= DIFF_PHASE (f)) at an arbitrary frequency f is used without using the value R of the phase difference spectrum DIFF_PHASE (F) linearly approximated at the Nyquist frequency F, By substituting F and R in Equation (3) with f and r, respectively, the difference D in reachable distance can be obtained. Then, the arithmetic processing unit 11 calculates the incident angle θ of the acoustic signal, that is, the angle θ indicating the direction in which it is estimated that the sound source (human) is present, using the calculated difference D of the reach distance (step S715).

  In addition, when estimating the direction in which a person who emits speech is present, it is determined whether or not the sound input is a speech section indicating the speech emitted by the person, and only when the speech input is determined to be a speech section. By executing the above process, the angle θ indicating the direction in which the sound source is estimated to exist may be calculated.

  Furthermore, even if it is determined that the SN ratio is larger than the predetermined value, if the phase difference is not assumed in view of the usage state, usage conditions, etc. of the application, the corresponding frequency or frequency band Is preferably excluded from the correction target of the phase difference spectrum at the current sampling time. For example, when the sound source direction estimating apparatus 1 according to the second embodiment is applied to a device that is supposed to speak from the front direction, such as a mobile phone, the direction θ in which the sound source is estimated with the front as 0 degree. However, when it is calculated that θ <−90 degrees or 90 degrees <θ, it is determined to be unexpected. In this case, the phase difference spectrum calculated up to the previous time is used without using the phase difference spectrum at the current sampling time.

  Furthermore, even if it is determined that the SN ratio is larger than a predetermined value, it is not preferable to estimate the direction of the target sound source in view of the usage state, usage conditions, etc. of the application. Is preferably excluded from selection targets. For example, when the target sound source is a voice produced by a human, there is no voice signal at a frequency of 100 Hz or less. Accordingly, 100 Hz or less can be excluded from the correction target.

  As described above, the sound source direction estimating apparatus 1 according to the second embodiment, when calculating the phase difference spectrum at a frequency or frequency band with a large SN ratio, is more than the phase difference spectrum calculated at the previous sampling time. The phase difference spectrum at the sampling time point (current sampling time point) is corrected with a weight, and when the SN ratio is small, the previous phase difference spectrum is corrected with a weight. By doing in this way, the newly calculated phase difference spectrum can be corrected sequentially. The corrected phase difference spectrum also reflects information on the phase difference at a frequency where the SN ratio at the past sampling time is large. Therefore, the phase difference spectrum does not vary greatly by being affected by the state of background noise, the change in the content of the acoustic signal emitted from the target sound source, and the like. Therefore, it is possible to calculate the incident angle of the acoustic signal, that is, the angle θ indicating the direction in which the target sound source is estimated to exist with high accuracy based on the difference D of the stable reach distance with higher accuracy. Note that the method of calculating the angle θ indicating the direction in which the target sound source is estimated to be present is not limited to the method using the distance difference D described above, and can be estimated with similar accuracy. Needless to say, there are various variations.

  Regarding the above first and second embodiments, the following additional notes are disclosed.

(Appendix 1)
An acoustic signal receiving means for receiving an acoustic signal from a sound source existing in a plurality of directions as an input of a plurality of channels and converting it into a signal on the time axis for each channel, and each signal on the time axis converted by the acoustic signal receiving means For each channel into a signal on the frequency axis, phase component calculation means for calculating the phase component of each channel signal on the frequency axis converted by the signal conversion means for each same frequency, and A phase difference calculation unit that calculates a phase difference between a plurality of channels using a phase component of each channel signal calculated for each same frequency by the phase component calculation unit, and a phase difference calculated by the phase difference calculation unit. Based on the reach distance difference calculating means for calculating the difference in the reach distance of the acoustic signal from the target sound source, and the reach distance difference calculating means. Based on the difference between the arrival distances, in the sound source direction estimation apparatus and a sound source direction estimating means for estimating a direction in which there is a target sound source,
Amplitude component calculating means for calculating the amplitude component of the signal on the frequency axis converted by the signal converting means;
Noise component estimation means for estimating a noise component from the amplitude component calculated by the amplitude component calculation means;
A signal-to-noise ratio calculating unit that calculates a signal-to-noise ratio for each frequency based on the amplitude component calculated by the amplitude component calculating unit and the noise component estimated by the noise component estimating unit;
Frequency extraction means for extracting a frequency at which the signal to noise ratio calculated by the signal to noise ratio calculation means is greater than a predetermined value;
The sound source direction estimating apparatus, wherein the reach distance difference calculating means calculates the reach distance difference based on the phase difference of the frequency extracted by the frequency extracting means.

(Appendix 2)
The frequency extracting means selects and extracts a predetermined number of frequencies in which the signal to noise ratio calculated by the signal to noise ratio calculating means is greater than a predetermined value in descending order of the calculated signal to noise ratio. The sound source direction estimation apparatus according to Supplementary Note 1, wherein

(Appendix 3)
An acoustic signal receiving unit that receives an acoustic signal from a sound source existing in a plurality of directions as an input of a plurality of channels and converts it into a sampling signal on the time axis for each channel, and each of the time axis converted by the acoustic signal receiving unit A signal conversion unit that converts the sampling signal into a signal on the frequency axis for each channel; a phase component calculation unit that calculates the phase component of each channel signal on the frequency axis converted by the signal conversion unit for each same frequency; A phase difference calculation means for calculating a phase difference between a plurality of channels using a phase component of each channel signal calculated for each same frequency by the phase component calculation means; and a phase calculated by the phase difference calculation means A reach distance difference calculating means for calculating a difference in reach of an acoustic signal from a target sound source based on the difference; Based on the difference between the arrival distances calculated by releasing difference calculation unit, in a sound source direction estimation apparatus and a sound source direction estimating means for estimating a direction in which there is a target sound source,
Amplitude component calculating means for calculating the amplitude component of the signal on the frequency axis converted at a predetermined sampling time by the signal converting means;
Noise component estimation means for estimating a noise component from the amplitude component calculated by the amplitude component calculation means;
A signal-to-noise ratio calculating unit that calculates a signal-to-noise ratio for each frequency based on the amplitude component calculated by the amplitude component calculating unit and the noise component estimated by the noise component estimating unit;
Correction means for correcting the calculation result of the phase difference at the sampling time based on the signal-to-noise ratio calculated by the signal-to-noise ratio calculation means and the calculation result of the phase difference at the past sampling time;
The sound source direction estimating device, wherein the reach distance difference calculating means calculates the reach distance difference based on the phase difference corrected by the correcting means.

(Appendix 4)
A voice section specifying means for specifying a voice section that is a section indicating a voice in the acoustic signal input received by the acoustic signal receiving means;
4. The supplementary note 1, wherein the signal converting unit converts only the signal of the voice section specified by the voice section specifying unit into a signal on a frequency axis. 5. Sound source direction estimation device.

(Appendix 5)
Accepting acoustic signals from sound sources that exist in multiple directions as input for multiple channels, converting them to signals on the time axis for each channel, and converting signals for each channel on the time axis to signals on the frequency axis And calculating the phase component of each channel signal on the converted frequency axis for each same frequency, and using the phase component of each channel signal calculated for each same frequency, the phase difference between multiple channels A step of calculating a difference in the reach distance of the acoustic signal from the target sound source based on the calculated phase difference, and a target sound source based on the calculated difference in the reach distance A sound source direction estimating method including the step of estimating an existing direction,
Calculating the amplitude component of the converted signal on the frequency axis;
Estimating a noise component from the calculated amplitude component;
Calculating a signal-to-noise ratio for each frequency based on the calculated amplitude component and the estimated noise component;
Extracting a frequency with a signal-to-noise ratio greater than a predetermined value, and
The sound source direction estimation method according to claim 1, wherein the step of calculating the difference of the reachable distances calculates the difference of the reachable distances based on the phase difference of the extracted frequencies.

(Appendix 6)
6. The sound source direction estimation according to claim 5, wherein the step of extracting the frequency includes selecting and extracting a predetermined number of frequencies having a signal-to-noise ratio larger than a predetermined value in descending order of the calculated signal-to-noise ratio. Method.

(Appendix 7)
Accepting sound signals from sound sources that exist in multiple directions as multi-channel inputs, converting them to sampling signals on the time axis for each channel, and converting each sampling signal on the time axis to a signal on the frequency axis for each channel A step of converting, a step of calculating the phase component of the signal of each channel on the converted frequency axis for each same frequency, and a phase component of the signal of each channel calculated for each same frequency between the channels. Calculating a phase difference of the acoustic signal from the target sound source based on the calculated phase difference, and calculating a difference in the target distance based on the calculated difference in the arrival distance. A sound source direction estimating method including a step of estimating a direction in which a sound source to be present exists,
Calculating the amplitude component of the signal on the frequency axis converted at a predetermined sampling time;
Estimating a noise component from the calculated amplitude component;
Calculating a signal-to-noise ratio for each frequency based on the calculated amplitude component and the estimated noise component;
Correcting the calculation result of the phase difference at the sampling time based on the calculated signal-to-noise ratio and the calculation result of the phase difference at the past sampling time, and
The step of calculating the difference in reach distance calculates the difference in reach distance based on the phase difference after correction.

(Appendix 8)
Further including the step of identifying a voice section that is a section indicating voice in the received acoustic signal input;
The step of converting into a signal on the frequency axis converts only the signal of the voice section specified in the step of specifying the voice section into a signal on the frequency axis. The sound source direction estimation method according to the item.

(Appendix 9)
An acoustic signal receiving means, which can be executed by a computer, accepts an acoustic signal from a sound source existing in a plurality of directions as an input of a plurality of channels, and converts it into a signal on a time axis for each channel, a time axis Signal conversion means for converting the signal of each upper channel into a signal on the frequency axis, phase component calculation means for calculating the phase component of each channel signal on the converted frequency axis for each same frequency, calculation for each same frequency The phase difference calculation means for calculating the phase difference between the plurality of channels using the phase component of the signal of each channel, and the difference in the reach of the acoustic signal from the target sound source based on the calculated phase difference Sound source direction for estimating the direction in which the target sound source exists based on the calculated reach distance difference calculation means and the calculated difference in reach distance In a computer program to function as a constant means,
The computer,
Amplitude component calculating means for calculating the amplitude component of the converted signal on the frequency axis;
Noise component estimation means for estimating a noise component from the calculated amplitude component;
Signal-to-noise ratio calculating means for calculating a signal-to-noise ratio for each frequency based on the calculated amplitude component and the estimated noise component, and a frequency at which the calculated signal-to-noise ratio is larger than a predetermined value Function as an extraction means,
The function as the reach distance difference calculating means calculates the difference in the reach distance based on the phase difference of the frequency extracted by the function as the frequency extracting means.

(Appendix 10)
The function as the frequency extraction means is such that a predetermined number of frequencies having a signal-to-noise ratio larger than a predetermined value are selected and extracted in descending order of the calculated signal-to-noise ratio. The computer program described.

(Appendix 11)
An acoustic signal receiving means, which can be executed by a computer, accepts an acoustic signal from a sound source existing in a plurality of directions as an input of a plurality of channels, and converts it into a signal on a time axis for each channel, a time axis Signal conversion means for converting each sampling signal to a signal on the frequency axis for each channel, phase component calculation means for calculating the phase component of each channel signal on the frequency axis converted for each same frequency, for each same frequency The phase difference calculation means for calculating the phase difference between a plurality of channels using the phase component of the signal of each channel calculated in step (b), and the arrival distance of the acoustic signal from the target sound source based on the calculated phase difference Based on the distance difference calculation means for calculating the difference and the calculated distance difference, the direction in which the target sound source exists is determined. In a computer program to function as the sound source direction estimation means for constant,
The computer,
An amplitude component calculating means for calculating the amplitude component of the signal on the frequency axis converted at a predetermined sampling time point;
Noise component estimation means for estimating a noise component from the calculated amplitude component;
Signal-to-noise ratio calculation means for calculating a signal-to-noise ratio for each frequency based on the calculated amplitude component and the estimated noise component, and calculation of the calculated signal-to-noise ratio and a phase difference at a past sampling time Based on the result, it functions as a correction means for correcting the calculation result of the phase difference at the time of sampling,
The function as the reach distance difference calculating means is configured to calculate the reach distance difference based on the phase difference corrected by the function as the correcting means.

(Appendix 12)
Causing the computer to function as a voice section specifying means for specifying a voice section that is a section indicating a voice in the received acoustic signal input;
Any one of appendices 9 to 11, wherein the function as the signal converting means is such that only the signal of the voice section specified by the function as the voice section specifying means is converted into a signal on the frequency axis. A computer program according to claim 1.

It is a block diagram which shows the structure of the general purpose computer which embodies the sound source direction estimation apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the function implement | achieved when the arithmetic processing part of the sound source direction estimation apparatus which concerns on Embodiment 1 of this invention runs a processing program. It is a flowchart which shows the process sequence of the arithmetic processing part of the sound source direction estimation apparatus which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the correction method of a phase difference spectrum at the time of selecting the frequency or frequency band whose SN ratio is larger than a predetermined value. It is a schematic diagram which shows the principle of the method of calculating the angle which shows the direction estimated that a sound source exists. It is a block diagram which shows the function implement | achieved when the arithmetic processing part of the sound source direction estimation apparatus which concerns on Embodiment 2 of this invention runs a processing program. It is a flowchart which shows the process sequence of the arithmetic processing part of the sound source direction estimation apparatus which concerns on Embodiment 2 of this invention. It is a flowchart which shows the process sequence of the arithmetic processing part of the sound source direction estimation apparatus which concerns on Embodiment 2 of this invention. It is a graph which shows an example of the correction coefficient according to S / N ratio.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sound source direction estimation apparatus 11 Arithmetic processing part 12 ROM
13 RAM
DESCRIPTION OF SYMBOLS 14 Communication interface part 15 Audio | voice input part 16 Audio | voice output part 17 Internal bus 201 Audio | voice reception part 202 Signal conversion part 203 Phase difference spectrum calculation part 204 Amplitude spectrum calculation part 205 Background noise estimation part 206 SN ratio calculation part 207 Phase difference spectrum selection part 208 Reaching distance difference calculating unit 209 Sound source direction estimating unit 210 Phase difference spectrum correcting unit

Claims (8)

An acoustic signal receiving means for receiving an acoustic signal from a sound source existing in a plurality of directions as an input of a plurality of channels and converting it into a signal on the time axis for each channel, and each signal on the time axis converted by the acoustic signal receiving means For each channel into a signal on the frequency axis, phase component calculation means for calculating the phase component of each channel signal on the frequency axis converted by the signal conversion means for each same frequency, and A phase difference calculation unit that calculates a phase difference between a plurality of channels using a phase component of each channel signal calculated for each same frequency by the phase component calculation unit, and a phase difference calculated by the phase difference calculation unit. Based on the reach distance difference calculating means for calculating the difference in the reach distance of the acoustic signal from the target sound source, and the reach distance difference calculating means. Based on the difference between the arrival distances, in the sound source direction estimation apparatus and a sound source direction estimating means for estimating a direction in which there is a target sound source,
Amplitude component calculating means for calculating the amplitude component of the signal on the frequency axis converted by the signal converting means;
Noise component estimation means for estimating a noise component from the amplitude component calculated by the amplitude component calculation means;
A signal-to-noise ratio calculating unit that calculates a signal-to-noise ratio for each frequency based on the amplitude component calculated by the amplitude component calculating unit and the noise component estimated by the noise component estimating unit;
Frequency extraction means for extracting a frequency at which the signal to noise ratio calculated by the signal to noise ratio calculation means is greater than a predetermined value;
The sound source direction estimating apparatus, wherein the reach distance difference calculating means calculates the reach distance difference based on the phase difference of the frequency extracted by the frequency extracting means.   The frequency extracting means selects and extracts a predetermined number of frequencies in which the signal to noise ratio calculated by the signal to noise ratio calculating means is larger than a predetermined value in descending order of the calculated signal to noise ratio. The sound source direction estimating apparatus according to claim 1, wherein the sound source direction estimating apparatus is provided. An acoustic signal receiving unit that receives an acoustic signal from a sound source existing in a plurality of directions as an input of a plurality of channels and converts it into a sampling signal on the time axis for each channel, and each of the time axis converted by the acoustic signal receiving unit A signal conversion unit that converts the sampling signal into a signal on the frequency axis for each channel; a phase component calculation unit that calculates the phase component of each channel signal on the frequency axis converted by the signal conversion unit for each same frequency; A phase difference calculation means for calculating a phase difference between a plurality of channels using a phase component of each channel signal calculated for each same frequency by the phase component calculation means; and a phase calculated by the phase difference calculation means A reach distance difference calculating means for calculating a difference in reach of an acoustic signal from a target sound source based on the difference; Based on the difference between the arrival distances calculated by releasing difference calculation unit, in a sound source direction estimation apparatus and a sound source direction estimating means for estimating a direction in which there is a target sound source,
Amplitude component calculating means for calculating the amplitude component of the signal on the frequency axis converted at a predetermined sampling time by the signal converting means;
Noise component estimation means for estimating a noise component from the amplitude component calculated by the amplitude component calculation means;
A signal-to-noise ratio calculating unit that calculates a signal-to-noise ratio for each frequency based on the amplitude component calculated by the amplitude component calculating unit and the noise component estimated by the noise component estimating unit;
Correction means for correcting the calculation result of the phase difference at the sampling time based on the signal-to-noise ratio calculated by the signal-to-noise ratio calculation means and the calculation result of the phase difference at the past sampling time;
The sound source direction estimating device, wherein the reach distance difference calculating means calculates the reach distance difference based on the phase difference corrected by the correcting means. A voice section specifying means for specifying a voice section that is a section indicating a voice in the acoustic signal input received by the acoustic signal receiving means;
The said signal conversion means converts only the signal of the audio | voice area specified by the said audio | voice area identification means into the signal on a frequency axis, The Claim 1 thru | or 3 characterized by the above-mentioned. Sound source direction estimation device. Accepting acoustic signals from sound sources that exist in multiple directions as input for multiple channels, converting them to signals on the time axis for each channel, and converting signals for each channel on the time axis to signals on the frequency axis And calculating the phase component of each channel signal on the converted frequency axis for each same frequency, and using the phase component of each channel signal calculated for each same frequency, the phase difference between multiple channels A step of calculating a difference in the reach distance of the acoustic signal from the target sound source based on the calculated phase difference, and a target sound source based on the calculated difference in the reach distance A sound source direction estimating method including the step of estimating an existing direction,
Calculating the amplitude component of the converted signal on the frequency axis;
Estimating a noise component from the calculated amplitude component;
Calculating a signal-to-noise ratio for each frequency based on the calculated amplitude component and the estimated noise component;
Extracting a frequency with a signal-to-noise ratio greater than a predetermined value, and
The sound source direction estimation method according to claim 1, wherein the step of calculating the difference of the reachable distances calculates the difference of the reachable distances based on the phase difference of the extracted frequencies. Accepting sound signals from sound sources that exist in multiple directions as multi-channel inputs, converting them to sampling signals on the time axis for each channel, and converting each sampling signal on the time axis to a signal on the frequency axis for each channel A step of converting, a step of calculating the phase component of the signal of each channel on the converted frequency axis for each same frequency, and a phase component of the signal of each channel calculated for each same frequency between the channels. Calculating a phase difference of the acoustic signal from the target sound source based on the calculated phase difference, and calculating a difference in the target distance based on the calculated difference in the arrival distance. A sound source direction estimation method including a step of estimating a direction in which a sound source to be present exists,
Calculating the amplitude component of the signal on the frequency axis converted at a predetermined sampling time;
Estimating a noise component from the calculated amplitude component;
Calculating a signal-to-noise ratio for each frequency based on the calculated amplitude component and the estimated noise component;
Correcting the calculation result of the phase difference at the sampling time based on the calculated signal-to-noise ratio and the calculation result of the phase difference at the past sampling time, and
The step of calculating the difference in reach distance calculates the difference in reach distance based on the phase difference after correction. An acoustic signal receiving means, which can be executed by a computer, accepts an acoustic signal from a sound source existing in a plurality of directions as an input of a plurality of channels, and converts it into a signal on a time axis for each channel, a time axis Signal conversion means for converting the signal of each upper channel into a signal on the frequency axis, phase component calculation means for calculating the phase component of each channel signal on the converted frequency axis for each same frequency, calculation for each same frequency The phase difference calculation means for calculating the phase difference between the plurality of channels using the phase component of the signal of each channel, and the difference in the reach of the acoustic signal from the target sound source based on the calculated phase difference Sound source direction for estimating the direction in which the target sound source exists based on the calculated reach distance difference calculation means and the calculated difference in reach distance In a computer program to function as a constant means,
The computer,
Amplitude component calculating means for calculating the amplitude component of the converted signal on the frequency axis;
Noise component estimation means for estimating a noise component from the calculated amplitude component;
Signal-to-noise ratio calculating means for calculating a signal-to-noise ratio for each frequency based on the calculated amplitude component and the estimated noise component, and a frequency at which the calculated signal-to-noise ratio is larger than a predetermined value Function as an extraction means,
The function as the reach distance difference calculating means calculates the difference in the reach distance based on the phase difference of the frequency extracted by the function as the frequency extracting means. An acoustic signal receiving means, which can be executed by a computer, accepts an acoustic signal from a sound source existing in a plurality of directions as an input of a plurality of channels, and converts it into a signal on a time axis for each channel, a time axis Signal conversion means for converting each sampling signal to a signal on the frequency axis for each channel, phase component calculation means for calculating the phase component of each channel signal on the frequency axis converted for each same frequency, for each same frequency The phase difference calculation means for calculating the phase difference between a plurality of channels using the phase component of the signal of each channel calculated in step (b), and the arrival distance of the acoustic signal from the target sound source based on the calculated phase difference Based on the distance difference calculation means for calculating the difference and the calculated distance difference, the direction in which the target sound source exists is determined. In a computer program to function as the sound source direction estimation means for constant,
The computer,
An amplitude component calculating means for calculating the amplitude component of the signal on the frequency axis converted at a predetermined sampling time point;
Noise component estimation means for estimating a noise component from the calculated amplitude component;
Signal-to-noise ratio calculation means for calculating a signal-to-noise ratio for each frequency based on the calculated amplitude component and the estimated noise component, and calculation of the calculated signal-to-noise ratio and a phase difference at a past sampling time Based on the result, it functions as a correction means for correcting the calculation result of the phase difference at the time of sampling,
The function as the reach distance difference calculating means is configured to calculate the reach distance difference based on the phase difference corrected by the function as the correcting means.

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